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AM49DL640AG70IT 데이터시트(PDF) 22 Page - Advanced Micro Devices |
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AM49DL640AG70IT 데이터시트(HTML) 22 Page - Advanced Micro Devices |
22 / 65 page April 1, 2003 Am49DL640AG 21 PR E L I M I N A R Y SecSi™ (Secured Silicon) Sector Flash Memory Region The SecSi (Secured Silicon) Sector feature provides a Flash memory region that enables permanent part identification through an Electronic Serial Number (ESN). The SecSi Sector is 256 bytes in length, and uses a SecSi Sector Indicator Bit (DQ7) to indicate whether or not the SecSi Sector is locked when shipped from the factory. This bit is permanently set at the factory and cannot be changed, which prevents cloning of a factory locked part. This ensures the secu- rity of the ESN once the product is shipped to the field. AMD offers the device with the SecSi Sector either f act ory l ocke d o r cu st om e r l ocka ble . T he f ac- tory-locked version is always protected when shipped from the factory, and has the SecSi (Secured Silicon) Sector Indicator Bit permanently set to a “1.” The cus- tomer-lockable version is shipped with the SecSi Sec- tor unprotected, allowing customers to utilize the that sector in any manner they choose. The customer-lock- able version has the SecSi (Secured Silicon) Sector Indicator Bit permanently set to a “0.” Thus, the SecSi Sector Indicator Bit prevents customer-lockable de- vices from being used to replace devices that are fac- tory locked. The system accesses the SecSi Sector Secure Sector through a command sequence (see “Enter SecSi™ Sector/Exit SecSi Sector Command Sequence”). After the system has written the Enter SecSi Sector com- mand sequence, it may read the SecSi Sector by using the addresses normally occupied by the boot sectors. This mode of operation continues until the system issues the Exit SecSi Sector command se- quence, or until power is removed from the device. On power-up, or following a hardware reset, the device re- verts to sending commands to the first 256 bytes of Sector 0. Note that the ACC function and unlock by- pass modes are not available when the SecSi Sector is enabled. Factory Locked: SecSi Sector Programmed and Protected At the Factory In a factory locked device, the SecSi Sector is pro- tected when the device is shipped from the factory. The SecSi Sector cannot be modified in any way. The device is preprogrammed with both a random number and a secure ESN. The 8-word random number will at addresses 000000h–000007h in word mode (or 000000h–00000Fh in byte mode). The secure ESN will be programmed in the next 8 words at addresses 000008h–00000Fh (or 000010h–000020h in byte mode). The device is available preprogrammed with one of the following: ■ A random, secure ESN only ■ Customer code through the ExpressFlash service ■ Both a random, secure ESN and customer code through the ExpressFlash service. Customers may opt to have their code programmed by AMD through the AMD ExpressFlash service. AMD programs the customer’s code, with or without the ran- dom ESN. The devices are then shipped from AMD’s factory with the SecSi Sector permanently locked. Contact an AMD representative for details on using AMD’s ExpressFlash service. Customer Lockable: SecSi Sector NOT Programmed or Protected At the Factory If the security feature is not required, the SecSi Sector can be treated as an additional Flash memory space. The SecSi Sector can be read any number of times, but can be programmed and locked only once. Note that the accelerated programming (ACC) and unlock bypass functions are not available when programming the SecSi Sector. The SecSi Sector area can be protected using one of the following procedures: ■ Write the three-cycle Enter SecSi Sector Region command sequence, and then follow the in-system sector protect algorithm as shown in Figure 2, ex- cept that RESET# may be at either V IH or VID. This allows in-system protection of the SecSi Sector Re- gion without raising any device pin to a high voltage. Note that this method is only applicable to the SecSi Sector. ■ To verify the protect/unprotect status of the SecSi Sector, follow the algorithm shown in Figure 3. Once the SecSi Sector is locked and verified, the sys- tem must write the Exit SecSi Sector Region com- mand sequence to return to reading and writing the remainder of the array. The SecSi Sector lock must be used with caution since, once locked, there is no procedure available for unlocking the SecSi Sector area and none of the bits in the SecSi Sector memory space can be modified in any way. |
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